This invention relates to a piezoelectric device.
Piezoelectric films can find extensive use in applications such as ink jet printing modules and surface acoustic devices. Piezoelectric films in ink jet printing modules can be capable of a large deflection when a voltage is applied. Applying a voltage can change the shape of the piezoelectric film in a jetting region of the print module, subjecting ink in the module to jetting pressure. Consequently, the jetting pressure can eject the ink from a pumping chamber and can deposit the ink on a medium. Piezoelectric films can be composed of lead zirconium titanate (xe2x80x9cPZTxe2x80x9d). Piezoelectric films can be formed by methods including, for example, physical vapor deposition techniques such as sputtering, chemical vapor deposition, or spin coating techniques such as a sol-gel method. Thicker piezoelectric films can be produced by increasing the time of deposition, by repeated deposition of individual films to build a thicker film, or by conventional bulk ceramic manufacturing methods.
A piezoelectric film can be prepared from an acicular seed crystal oriented on a substrate. The film is grown from the acicular seed crystal. The piezoelectric film grown from the acicular seed crystal can have d-coefficients that are improved relative to films grown from a symmetric seed crystal or a non-oriented seed crystal.
A seed crystal is a crystalline material that nucleates growth of a bulk crystal or crystalline film. An acicular seed crystal is a non-spherical crystal.
In one aspect, a method for manufacturing a piezoelectric device includes placing an acicular seed crystal onto a substrate, orienting the acicular seed crystal on the substrate, and growing a piezoelectric film from the acicular seed crystal. The seed crystal can be placed onto the substrate by depositing the seed crystal onto the substrate. The seed crystal can be oriented by inducing a flow of a precursor including the seed crystal on the substrate. The inducing of the flow of a precursor includes spin-coating or dip-coating the precursor on the substrate. The precursor can be a sol. Orienting the seed crystal includes spin-coating a sol on the substrate. The growing of the piezoelectric film includes forming a gel.
The acicular seed crystal can be a single crystal. The acicular seed crystal can have a length substantially parallel to the surface of the substrate. The seed crystal has an aspect ratio is greater than 1.5:1, greater than 2:1, or greater than 2.4:1. The acicular seed crystal can be a platelet. The method can further include placing a second acicular seed crystal onto a substrate, orienting the second seed crystal on the substrate, and growing a piezoelectric film from the second acicular seed crystal.
The piezoelectric film in the ink jet printing module can have a thickness in the range from about 0.1 to 25 microns, in the range from 0.5 to 10 microns, or from 0.1 to 5 microns. The piezoelectric film can be poled or annealed. The film can include lead zirconium titanate.
In another aspect, an ink jet printing module includes a substrate and a piezoelectric film on the substrate, the film including a plurality of acicular seed crystal oriented in substantially the same direction on the substrate. Each seed crystal can have a length substantially parallel to a surface of the substrate. The substrate can be silicon. The ink jet printing module includes an ink channel and electrical contacts arranged for activation of the piezoelectric film. The piezoelectric film is positioned to fill the channel with ink and subject the ink to jetting pressures during activation.
In another aspect, a method of manufacturing an ink jet printing module includes depositing a seed crystal in proximity to a surface, arranging the seed crystal so that the length is substantially parallel to the surface, and growing a piezoelectric film from the seed crystal. When in proximity to a surface, the seed crystal can contact or nearly contact the surface. The crystal has a length, a thickness and an aspect ratio greater than 1.1:1. The surface is a portion of the substrate. The seed crystal can be arranged so that the length is substantially parallel to the surface which includes a flow of a precursor including the seed crystal on the surface. The seed crystal can be arranged by inducing a flow of precursor including the seed crystal, for example, by spin-coating or dip-coating. The precursor can be a sol. In the method, inducing the flow of the precursor can include spin-coating of the sol.
Details are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.